Excimer lasers, that are currently widely used in the semiconductor industry for lithography applications, arc pulsed, transversal, excited gas discharge lasers. The major interest of this industry is the reliability, uptime, and mean time to repair (MTTR) the laser system. If a failure occurs, it must be repaired quickly. Accordingly, diagnosis of a failure in the laser system has to be performed in a short time and the defective part of the system has to be identified and repaired or replaced immediately.
For a pulsed laser, the generation of the light energy, from an externally applied trigger pulse to the ultimate light pulse is critical. Particularly in lithography, it is very important that one light pulse is generated for each trigger pulse. In operation, sometimes more or less output pulses will be generated for each trigger pulse. In the past, when a failure occurred, a service person was required to manually analyze each part of the trigger chain. This analysis was strongly dependent on the experience and knowledge of the service engineer. Usually the engineer checked the input and output of each module to trace where the fault occurred. This process is quite time consuming and difficult. Therefore, it is desirable to have an automated system that can check for faults in the trigger chain of a pulsed laser and report where the fault is located in order to reduce the down time of the laser.